Wiring – Where to put the doorbell transformer for new wired doorbell in old house

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I used to have an old whole house intercom system with an integrated transformer inside the kitchen wall, far from the front doorbell. For the new basic doorbell, I was planning to power the doorbell transformer from the dining room receptacle just inside the front door, and put the chime just above there.

But, I just can't think of a good place (or right place) to put the doorbell transformer. I understand it is usually not inside a wall or in a junction box, but somewhere visible. Since this is old work, I can't easily run doorbell wire very far to put it in an attic or garage or closet.

Ideas:

  • In the dining room wall and attached to the outside of an existing junction box?
  • In the dining room wall and in its own junction box?
  • In the dining room wall and attached to a stud?
  • On the outside of the wall in the dining room and hidden behind something like a doorbell chime cover (my wife wants me to make one for the chime anyway)

Any ideas from DIYers or electricians? Thanks!

Best Answer

Generally, you are controlled by where the existing wiring is located.

Mounting a new transformer has to follow Code and its labeling and instructions, particularly where the AC mains side of the transformer is concerned. The 24V low-voltage wiring can follow the relaxed rules for low-voltage power, and be installed like thermostat wire. Here are 2 popular form-factors for 24V transformers:

  • Mounts to a knockout on the side of a metal box. AC mains wiring is inside the box, 24V is outside. Obviously this requires a metal box somewhere whose sides are exposed.
  • Mounts on the face of a 4x4 metal box, replacing the normal lid. Again AC mains is on one side, low voltage on the other.

Obviously both of these mounting types require unfinished "utility space" in your home where such things are not an aesthetic misfit. It's all the rage these days to destroy all utility space in homes in a mad quest for more listable square footage to puff up resale value. Unfortunately those people have painted themselves into a corner, tough luck for them.

You can also simply grab 24 VAC from the furnace transformer, from its R and C terminals (also available at the thermostat sometimes). It is usually oversized enough it doesn't mind a watt or two for a Ring camera. Transformers are very tolerant of short term overloads, their limiting factor being internal heat, so the short load of a doorbell chiming won't bother it at all.

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